1. Field of the Invention
The present invention relates to a magnetic composition, more particularly to an organic magnetic composition comprising an alkali-metal-doped tetraazaporphyrin derivative or an alkali-metal-doped porphyrin derivative, for example, for use in magnetic toners and inks.
The present invention also relates to a magnetic toner comprising the organic magnetic composition for developing latent electrostatic images in electrophotography, electrostatic recording and electrostatic printing; and to a magnetic ink comprising the organic magnetic composition, for use with ink jet printers, hot-melt printers and thermal image transfer ink ribbons, and for use with instruments for writing in general use.
The magnetic composition of the present invention can also be employed as an absorbing material, a shielding material, a material for a filter, and also can be employed in an ultra-high-frequency apparatus, and a magnetism-controlling apparatus.
2. Discussion of Background
Magnetic materials are widely used, for example, as magnetic materials with high magnetic permeability such as permanent magnet; magnetostrictive materials; and acoustic materials, in various fields such as the fields of electric and electronic appliances, automobiles, appliances for medical service, communication apparatus, and materials for magnetic recording.
Organic magnetic materials have various advantages over inorganic magnetic materials, in particular, in that organic magnetic materials have smaller densities than those of inorganic magnetic materials, and exhibit better dispersibilities in binder agents than those of inorganic magnetic materials, and that many of organic magnetic materials assume a white or light pale color. Thus, recently, great attention has been paid to the development of such organic magnetic materials.
More specifically, as such organic magnetic materials, there have been reported, for example, a black powder-like polymer which was obtained by heating 4,4'-(butadiyne-1,4-diyl)-bis(2,2,6,6-tetramethyl-4 -hydroxy-piperidine-1-oxyl) or subjecting the same to ultraviolet-light irradiation [Korshak et al., Nature 326 370 (1987)], a black insoluble polymer obtained by polymerizing 1,3,5-triaminobenzene by use of iodine [Torrance, Synth. Metal, 19 709 (1987)], and polycarbene [Iwamura et al., Chemical Society of Japan, 1987, No. 4595].
These organic magnetic materials, however, are difficult to synthesize and have problems in the reproducibility of the syntheses thereof. Furthermore, only several percents of the moieties of these organic magnetic materials exhibit ferromagnetism, and the temperatures at which these organic magnetic materials exhibit magnetism are extremely low. In addition, these organic magnetic materials are unstable in air, so that they still have problems to be solved as magnetic materials for use in practice.
Ohtani et al. have proposed in Japanese Laid-Open Patent Applications 62-521 and 62-522 an organic magnetic material comprising a polycondensate of fused polynuclear aromatics resin (COPNA) which was synthesized from a condensed polycyclic aromatic compound by use of p-xylene glycol. They have further proposed in Japanese Laid-Open Patent Application 62-282080 an organic magnetic material comprising a thermosetting resin having higher heat resistance than that of the above-mentioned polycondensate of fused polynuclear aromatics resin (COPNA), which was prepared by replacing the p-xylene glycol with benzaldehyde or benzenedialdehyde in the procedure of the synthesis of the polycondensate of fused polynuclear aromatics resin (COPNA).
It has been reported that the above-mentioned organic magnetic materials exhibit ferromagnetism at room temperature. However, it has been found that the polymeric structures of the above resins are not known exactly and the reproducibility of the exhibition of the ferro-magnetism of the above resins is extremely poor.
As organic magnetic materials of a metal complex type, there have been synthesized polynuclear metal complexes of a different-metal alternate coordination type, having a one or more dimensional chain structure, for example, as disclosed in Japanese Laid-Open Patent Application 4-74193, J. Am. Chem. Soc., 110., 782 (1988), and J. Chem. Soc., Chem. Commun., 642 (1988).
L. S. Grigoryan et al. (L. S. Grigoryan is one of the joint co-inventors of the present invention) have already reported that organic magnetic materials were synthesized by doping metal-phthalocyanine by alkali metals.
Furthermore, a magnetic polymer complex salt, PPH-H.sub.2 SO.sub.4, in which PPH stands for poly(2,6-pyridinediyl methylidene nitrilohexamethylene nitrilomethylidene), has been synthesized by allowing PPH to react with ferrous sulfate, as disclosed in Japanese Laid-Open Patent Applications 1-118515, 1-96215, 1-96216, 1-99217, 2-55765, 63-205666, 1-277251, 1-277252, 1-277253, 4-191091, and Solid State Physics Vol. 18, No. 5 (1983).
By use of a tetraazaporphyrin derivative which is employed as a moiety of the alkali-metal-doped tetraazaporphyrin derivative for use in the present invention, it has been tried to synthesize a magnetic polytetraazaporphyrin iron complex, for instance, as disclosed in Japanese Laid-Open Patent Application 62-192383, and a charge-transfer type magnetic material as disclosed in Adv. Mater., 498 (1992).
These magnetic materials, however, have lower Curie temperatures than that of the magnetic composition of the present invention, and exhibit extremely poor reproducibility of the ferromagnetism at room temperature, so that these magnetic materials cannot be employed in practice.
As mentioned previously, magnetic materials are widely employed in various fields. For example, magnetic materials are employed in magnetic toners.
A magnetic toner is employed as a developer for a development method using a mono-component magnetic toner for developing latent electrostatic images formed on an electrophotographic photoconductor which is composed of an electroconductive support and a photoconductive layer provided thereon, or on an electrostatic recording medium which is composed of an electroconductive support and a dielectric layer provided thereon.
In this development method, an electroconductive magnetic toner is held on an electroconductive and non-magnetic carrier sleeve through an inner magnet which is built within the carrier sleeve, and the magnetic toner is transferred onto latent electrostatic images formed on a latent-electrostatic-image bearing member comprising an electroconductive support, by the relative movement of the carrier sleeve and the magnet.
When the magnetic toner is thus transferred onto the latent electrostatic images, electroconductive paths are formed between the electroconductive support of the latent-electrostatic-image bearing member and the carrier sleeve, and also between the electroconductive support and the magnetic toner, so that electric charges with a polarity opposite to that of the latent electrostatic images are induced in the magnetic toner for the development of the latent electrostatic images.
However, an electroconductive toner for use in the above-mentioned charge induction development exhibits poor image transfer performance at high humidities and therefore it is difficult to use plain paper as a transfer sheet for such an electroconductive toner, so that recently a development method using a magnetic toner of a triboelectric charging, high resistivity type is mainly used.
Furthermore, the development method using a mono-component magnetic toner has attracted attention because copying apparatus for use with a mono-component magnetic toner can be reduced in size and cost. In addition, a color development by use of mono-component magnetic toners has also attracted attention in accordance with recent development of multi-color copy image formation methods.
In accordance with the recent remarkable increase of the quantity of information to be handled, there is a strong demand for high speed processing in copying machines and printers.
The magnetic materials can also be used in magnetic inks which are generally composed of a magnetic material, a dye, a vehicle composed of a resin and a carrier medium, and additives. Such magnetic inks are used, for example, in oil inks, aqueous inks, and hot-melt inks. More specifically, inks composed of a magnetic material and an organic solvent such as kerosene or glycerin, or water, in which the magnetic material is dispersed in the form of colloidal particles, are disclosed in Japanese Laid-Open Patent Application 59-147217; and an ink composed of a magnetic material and wax in which the magnetic material is dispersed is disclosed in Japanese Laid-Open Patent Application 62-267379.
Some organic magnetic materials are excellent with respect to the reproducibility of ferromagnetism, but the temperatures at which the excellent reproducibility of ferromagnetism is exhibited are limited to too low temperatures to be used in practice, or the syntheses thereof are too complicated to be used in practice. Other organic magnetic materials exhibit ferromagnetism at room temperature, but the reproducibility of the exhibition of the ferromagnetism at room temperature is too poor to be used in practice. Thus, organic magnetic materials that can be satisfactorily used in practice have not yet been obtained.
In conventional mono-component magnetic toners, inorganic magnetic materials such as ferrite and magnetite are employed as the magnetic materials for the mono-component magnetic toners. A mono-magnetic toner prepared by dispersing such an inorganic magnetic material in a binder resin has the shortcoming that the toner is too fragile to be stirred in a development unit or too fragile to be treated even in a toner production system, because it is extremely difficult to disperse the inorganic magnetic material uniformly in a binder resin.
Furthermore, the densities of the inorganic magnetic materials such as ferrite and magnetite are generally 3 g/cm.sup.3 or more, and the magnetic materials for use in the mono-component magnetic toner have a density in a range of 5 to 6 g/cm.sup.3. Therefore a mono-component magnetic toner comprising such a magnetic material in an amount in a range of 20 to 80 wt. % has too high a density to handle as a toner and to be stirred in a development unit, and requires a large amount of driving energy. Furthermore, a magnetic toner with such a high density has the problem that it is scattered when rotated with high speed because of the centrifugal force exerted on the toner.
In conventional magnetic inks, a magnetic material therefor comprises a metallic oxide such as ferrite, chromium oxide, a Mn-B alloy, a Mn-Al alloy, an Fe-Ni alloy, or a Sn-Fe alloy, so that the compatibility of such a magnetic material with a vehicle for the magnetic inks is so poor that the magnetic material tends to aggregate and is difficult to be dispersed in the vehicle. Furthermore, images formed by such magnetic inks, when dried, tend to be cracked. In addition, it is difficult for such magnetic inks to have the color of a pigment or dye employed therein because the magnetic materials employed therein have dark colors such as black, dark brown and brown.